An electronic circuit may include a processor for processing, handling, communicating or otherwise manipulating information. Modern electronic circuits often take the form of integrated circuits (ICs) that incorporate several functional circuit blocks together on a common semiconductor die. Manufacturing test systems may monitor and separate integrated circuits (ICs) by functional capability such as the speed or frequency at which a circuit functions without error or failure. Manufacturing procedures may sort integrated circuits by specific operating parameters. For example, a test process may check integrated circuits for speed and discard integrated circuits that test slow. The test process may alternatively separate integrated circuits into categories of circuits, for example circuits useful in slower speed applications and circuits useful in higher speed applications. Manufacturing systems may also test for integrated circuit parameters other than speed or frequency response, for example thermal response, inducible noise sensitivity and immunity, and power supply voltage response. Integrated circuits often incorporate a built-in self-test (BIST) capability that is especially useful in testing complex integrated or electronic circuits. Built-in test (BIST) hardware or firmware in integrated circuits may employ complex internal test patterns, functional array and discrete logic test programs, and structured test techniques. Built-in test programs in an integrated circuit may test combinational and sequential logic, processor elements, memory, embedded logic structures and other elements of complex circuits.
Integrated circuits may exhibit faster execution capability by increasing the frequency of clocks within or external to the integrated circuit. A particular integrated circuit may also exhibit superior functionality in comparison with another integrated circuit, if the particular integrated circuit operates at the same frequency as the other integrated circuit, but at a lower voltage. By requiring less voltage, the particular integrated circuit requires less power than the other integrated circuit. Typically an integrated circuit that operates at higher frequencies than the average same-type integrated circuit without failure will also operate at a lower voltage than the average same-type integrated circuit. Determining critical device parametric values may require a complex test strategy and typically involves extensive testing over a large sampling of devices.
What is needed is a testing method and apparatus that addresses the problems faced by integrated circuit manufacturer described above.